This invention is directed generally to the field of medical testing or monitoring electrodes and more particularly to a headband-carried electrode system particularly suited for non-invasive alcohol/drug analysis.
Electrodes of various types are placed on the external surfaces of the body for purposes of performing a number of medical tests or analysis procedures. The present invention relates to a novel system or apparatus for placing a number of electrodes about the forehead region of the body to accomplish such medical testing, as for example measuring the corneo-retinal potential of a subject.
A body of data has been empirically developed relating the corneo-retinal potential to the presence in the body of varying levels of controlled substances. More particularly, it has been proposed to utilize this body of data and such measurements to assess the presence in the body of alcohol and/or a number of frequently abused substances, such as barbiturates, tranquilizers, opiates, and hallucinogens.
That is to say, each substance will produce a particular type of waveform which is unique to that substance. Hence, the waveform obtained from a suspected individual may be essentially "compared" to the known waveforms from the empirical data to determine whether or not the subject is under the influence or is otherwise impaired by a drug and/or alcohol. Additionally, the configuration of the waveform will identify the particular substance involved be it alcohol, amphetamines, barbiturates, tranquilizers, opiates, cocaine, or hallucinogens including PCP and marijuana.
Such testing has heretofore been carried out using three electrodes attached to the forehead of the subject. The first or central electrode is substantially centrally placed upon the forehead. An additional two side or temporal electrodes are placed at predetermined positions relative to the temporal lobes of the forehead of the subject. The proper placement of the electrodes is believed important in obtaining reliable results. Moreover, it has been found that there is a wide range of variance among individuals as to the proper locations of the temporal electrodes relative to the forehead and relative to the center electrode. For example, it has been found that both the vertical and the lateral distances between the temporal electrodes and the center forehead electrode (the vertical distance being the difference in elevation) tend to decrease with decreasing head size. Conversely, these distances tend to increase with increasing head size of the subject.